IC A School – Airflow, H2S, Refrigerant Practice Test

Indication and control panels run on a DC power source because it reliably powers meters, lights, alarms, sensors, and relay coils. A 24 VDC battery is used because it provides enough voltage to drive these loads without requiring excessive current or bulky wiring, while staying within a safe, standard level for industrial control components. 24 VDC is a common, readily available standard for such panels, making it easy to source relays, PLC inputs, and indicators that all expect that voltage. Using 12 VDC would mean higher current for the same power, increasing wiring and heat; 5 VDC is typically reserved for microelectronics rather than powering the whole panel; and 120 VAC would be mains power rather than a battery voltage, which changes safety and isolation requirements.